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Optical absorption in complexes of abasic DNA with noble-metal nanoclusters by first principles calculations
摘要： Optical absorption in complexes of abasic DNA with noble-metal nanoclusters by first principles calculations. Abasic sites (AP site) in a DNA duplex have been experimentally used to produce fluorescent Ag nanoclusters (NC) with a small number of atoms (n ≤ 6). These AP-DNA:NC complexes act as biological markers that help to locate genes associated with diseases related to single nucleotide polymorphisms (SNP), for example. Abasic sites are the most common SNP genetic variation, and their detection may help predict a host of genetically determined diseases. In this work, we report a theoretical study of the optical absorption spectra of AP-DNA:Ag4 and AP-DNA:Au4 complexes using a fully ab initio methodology. We consider several different base environments for the noble-metal nanocluster occupying the AP site, and compute the absorption spectra of sixteen AP-DNA:Ag4 and sixteen AP-DNA:Au4 complexes. We find that optical absorption in the AP-DNA:Ag4 complexes tends to concentrate in the green-to-violet range of frequencies (2.50 eV ≤ ?ω ≤ 3.2 eV) and that AP-DNA:Au4 complexes display absorption peaks in the violet-to-ultraviolet interval (?ω ≥ 3.0 eV). An analysis of the optical absorption mechanisms in these AP-DNA:NC complexes shows that they can be of local, charge-transfer, or hybrid nature, i.e., AP-DNA:NC complexes display the full variety of optical absorption processes in molecular systems. In particular, we identify both charge-transfer and hybrid processes involving several DNA bases surrounding the NC. Importantly, we find that even sequences where the Ag4 cluster is not in a guanine rich neighborhood display absorption peaks in the visible-light spectrum. Moreover, we obtain that the maximum intensities of the absorption peaks in complexes with pyrimidine vacancies are generally higher than those in complexes with purine vacancies. Regarding the selectivity of single-vacancy AP-DNA to specific noble-metal nanocluster sizes, our calculations show that the four-atom Ag4 (Au4) species fits naturally and binds into the AP-site in a single-vacancy AP-DNA.
关键词： noble-metal nanoclusters,optical absorption,first principles calculations,abasic DNA,Au4,charge-transfer,hybrid processes,Ag4
更新于2025-09-19 17:15:36
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Janus Chromium Dichalcogenides Monolayers with Low Carrier Recombination for Photocatalytic Overall Water-Splitting under Infrared Light
摘要： Photocatalytic overall water-splitting is known as one of most promising methods to alleviate energy crisis. Searching for stable and efficient photocatalysts plays a critical role in this process. Here, we propose a novel class of Janus chromium dichalcogenides (CrXY, X/Y = S, Se, Te) monolayers serving as efficient photocatalysts for overall water-splitting under infrared light irradiation. We reveal that these Janus monolayers harbor an intrinsic dipole, which promotes the spatial separation of photo-generated carriers. More significantly, these systems exhibit suitable band gaps as well as band edge positions, enabling preeminent infrared optical absorption and high carrier mobility. Furthermore, the nonradiative recombination of photoinduced charge carriers in CrXY monolayers are evaluated based on time-domain density functional theory. The obtained long-lived excited carriers (~ 2 ns) are even comparable with that in transition-metal dichalcogenides heterostructures, which benefits for the photocatalytic reaction with high efficiency. Our results provide a new guidance for designing brand new photocatalytic systems with broad optical absorption and low carrier recombination.
关键词： infrared light,first principles calculations,carrier recombination,Janus chromium dichalcogenides,photocatalytic water-splitting
更新于2025-09-19 17:15:36
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Tuning the electronic properties of van der Waals heterostructures composed of black phosphorus and graphitic SiC
摘要： This study presents a new van der Waals (vdW) heterostructure composed of monolayer black phosphorus (BP) and monolayer graphitic SiC (g-SiC). Using first-principles calculations, the structural and electronic properties of the BP/SiC heterostructure were investigated. It was found that by stacking BP with SiC, weak type-I band alignment can be achieved with a band gap of 0.705 eV, where the direct band gap as well as linear dichroism features were well preserved. The electrostatic potential drop in the heterojunction was calculated to be 4.044 eV. By applying perpendicular electric field, the band alignment can be altered to either type-I or type-II, and the band gap can be effectively controlled by field intensity, hence making the heterostructure suitable for various applications.
关键词： first-principles calculations,van der Waals heterostructure,graphitic SiC,electronic properties,black phosphorus
更新于2025-09-19 17:15:36
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A novel hydrogenated boron–carbon monolayer with high stability and promising carrier mobility
摘要： Although immense research on the extension of the two-dimensional (2D) material family has been carried out, 2D materials with a satisfactory band gap, high carrier mobility, and outstanding thermodynamic stability under ambient conditions are still limited. In this work, using first principles calculations, we proposed new 2D ternary materials consisting of C, B, and H atoms, namely hexagonal-BCH (h-BCH) and tetragonal-BCH (t-BCH). Both phonon calculations and ab initio molecular dynamics simulations show that these proposed sheets are thermodynamically stable phases. The electronic structure calculations indicate that h-BCH and t-BCH sheets are semiconductors with a band gap of 2.66 and 2.22 eV, respectively. Remarkably, the h-BCH (t-BCH) sheet exhibits electron mobility as high as 7.41 × 10^3 (1.09 × 10^3) cm^2 V^{-1} s^{-1}, which is higher than that of the MoS2 monolayer, though the hole mobility is about one (two) order of magnitude lower. Equally important is the fact that the position of both the conduction and valence band edges of the h-BCH sheet matches well with the chemical reaction potential of H2/H+ and O2/H2O, giving a 2D photocatalyst as a potential candidate for overall visible-light-driven water splitting. Therefore, the designed h-BCH and t-BCH monolayers have promising applications in future electronics and photocatalysts.
关键词： 2D materials,boron-carbon-hydrogen,photocatalysis,first principles calculations,carrier mobility
更新于2025-09-19 17:15:36
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Room temperature ferromagnetism in ball milled Cu-doped ZnO nanocrystallines: an experimental and first-principles DFT studies
摘要： Experimental and theoretical studies on the room temperature ferromagnetism of ball milled Zn0.95Cu0.05O nanocrystalline, were reported. X-ray diffraction analysis reveals that the most dominant crystalline phase is hexagonal wurtzite with presence of weak peaks due to Cu and CuO. Rietveld analysis indicated that the crystallite size decreases with increasing milling time, while the strain enhanced with milling time. Magnetic measurements using SQUID expose remarkable room temperature ferromagnetic ordering for milled samples. The physical origin of the ferromagnetism order has been explained using a bound magnetic polaron model. Theoretical calculations based on First principles methods were employed to calculate the electronic structures and magnetic properties of Cu doping and zinc and oxygen vacancies behavior of Zn1?xCuxO. It was found that a Cu dopant leads to induce magnetism and exhibits an increasing of magnetic moment when Zn vacancy are introduced.
关键词： Room temperature ferromagnetism,Ball milled Cu-doped ZnO,Magnetic properties,Nanocrystalline,First-principles DFT
更新于2025-09-19 17:13:59
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Thickness dependence of solar cell efficiency in transition metal dichalcogenides MX2 (M: Mo, W; X: S, Se, Te)
摘要： Bulk transition metal dichalcogenides are indirect gap semiconductors with optical gaps in the range of 0.7–1.6 eV, which makes them suitable for solar cell applications. In this work, we study the electronic structure, optical properties, and the thickness dependence of the solar cell efficiencies of MX2 (M: Mo, W; X: S, Se, Te) with density functional theory and GW t BSE. Through this analysis, we find a change in solar cell efficiency trends at slab thicknesses of 3 μm. For thin films solar cells (thicknesses smaller than 3 μm), the tellurides present the highest efficiencies (about 20% for a 100 nm thick slab). In contrast, for thicknesses greater than 3 μm, our results indicate that a maximum solar cell efficiency can be achieved in WS2. For instance, a 100 μm slab of WS2 presents a solar cell efficiency of 36.3%, making this material a promising candidate for solar cell applications.
关键词： Thin film,First-principles,DFT,Solar cell,Transition metal dichalcogenides,GWtBSE
更新于2025-09-19 17:13:59
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Understanding Molecular Adsorption on CuSCN Surfaces Toward Perovskite Solar Cell Applications
摘要： CuSCN has been employed as the hole transporting material for solar cells and it is established to offer superior power conversion efficiencies and stabilities of the perovskite solar cell. In this manuscript, we carry out first principles calculations to understand the structures and properties CuSCN surfaces in the presence of small molecules that are common in the solution processable solar cells. The molecular adsorbates include additives, precursors and solvents to synthesize the halide perovskite solar cell components such as methylammonium iodide (MAI), lead iodide (PbI2), acetonitrile, chloroform, dimethylformamide (DMF), dimethylsulfoxide (DMSO), methanol and ethanol. The study suggests that the CuSCN surfaces interact with these additive molecules in various degrees and such adsorption is strongly dependent on the CuSCN surface directions. The presence of the PbI2 moiety leads to additional empty states inside the band gap of CuSCN. The presence of the molecular adsorbates impacts on the electronic and optical properties of the CuSCN surfaces, and further additive-based interfacial engineering approach of the perovskite/CuSCN system is called for. This study paves the way toward the fundamental understanding of the CuSCN surfaces toward optoelectronic applications.
关键词： perovskite solar cells,optoelectronic applications,CuSCN,molecular adsorption,first principles calculations
更新于2025-09-19 17:13:59
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Growth and optical properties of a new stoichiometric laser crystal Pr(BO2)3
摘要： Single crystal Pr(BO2)3 with a centimeter size was grown successfully by a flux method using 3Li2CO3-2H3BO3 as a flux. The absorption spectrum, emission spectrum, and luminescence lifetime of Pr(BO2)3 crystal were measured. The Pr(BO2)3 crystal has a relatively large absorption cross section and full widths at half maximum (FWHM), which is advantageous for the crystal to absorb enough energy from the pumping source. The spectrum parameters were calculated based on Judd–Ofelt (J-O) theory, and the effective J-O parameters were determined as: Ω2=37.47×1020 cm2, Ω4=6.80×1020 cm2, and Ω6=1.05×1020 cm2. Furthermore, the emission cross sections for the 3P0→3F2 transition at 650 nm was calculated to be 13.6×10-19 cm2. The fluorescence lifetime of 3P0 level was obtained to be 4.5 ns. The Raman spectrum of the crystal was also analyzed in detail. Physical properties such as thermal and chemical stability, hardness, and cleavage properties were explored. The refractive index and electronic structure were calculated by the first-principles method.
关键词： first-principles,Pr(BO2)3,J-O theory,optical properties,crystal growth
更新于2025-09-19 17:13:59
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Coupled structural distortions, domains, and control of phase competition in polar
摘要： Materials with coupled or competing order parameters display highly tunable ground states, where subtle perturbations reveal distinct electronic and magnetic phases. These states generally are underpinned by complex crystal structures, but the role of structural complexity in these phases often is unclear. We use group-theoretic methods and first-principles calculations to analyze a set of coupled structural distortions that underlie the polar charge and orbitally ordered antiferromagnetic ground state of A-site ordered SmBaMn2O6. We show that these distortions play a key role in establishing the ground state and stabilizing a network of domain wall vortices. Furthermore, we show that the crystal structure provides a knob to control competing electronic and magnetic phases at structural domain walls and in epitaxially strained thin films. These results provide new understanding of the complex physics realized across multiple length scales in SmBaMn2O6 and demonstrate a framework for systematic exploration of correlated and structurally complex materials.
关键词： phase competition,first-principles calculations,domains,coupled structural distortions,group-theoretic methods,polar SmBaMn2O6
更新于2025-09-16 10:30:52
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Size-controlled excitonic effects on electronic and optical properties of Sb <sub/>2</sub> S <sub/>3</sub> nanowires
摘要： In this work, the electronic and optical properties of one-dimensional (1D) Sb2S3 nanowires (NWs) with different sizes are investigated using first-principles calculations. The indirect–direct band transition of Sb2S3 NWs can be tuned effectively by the NW size and various uniaxial strains. In the Sb2S3 NWs, the quantum confinement effects result in wider bandgaps while the significantly enhanced electron–hole interaction that is expected to produce excitonic bound states generates a bandgap narrowing. The exciton binding energies for the Sb2S3 NWs are predicted by the effective masses of electrons and holes to lie in the range of 0–1 eV, which are larger than that of bulk Sb2S3, suggesting that excitons in Sb2S3 NWs may bind possible defects to promote luminescence. The size-controlled absorption edge blueshift and redshift of Sb2S3 NWs suggest that Sb2S3 NWs may be promising in the applications of nanoscale light emitting devices.
关键词： optical properties,first-principles calculations,quantum confinement effects,light emitting devices,electronic properties,exciton binding energies,Sb2S3 nanowires
更新于2025-09-16 10:30:52